JPS6271973A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent an image forming device from useless print formation or useless image forming operation by executing rescanning with an original scanning means when the 1st abnormal scanning state is detected, and at the detection of the 2nd abnormal scanning state, discharging transfer paper. CONSTITUTION:The scanning speed of plural times of scanning is always super vised, and if abnormality is detected in the scanning speed, scanning is retried again so that a fine color print prevented from color shear or hue shear is obtained and the formation of useless failed prints is suppressed. When a reader detects the generation of color shear more than an allowable value, the reader intermits the image forming cycle of a printer at the time of detection the outputs the same color again from the reader. When the color shear is included within the allowable value, the intermitted image formation cycle is restarted and continued to complete a required image forming process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an image forming type for forming an image on a Q medium, and relates to an image forming apparatus suitable for use in, for example, color copying.

[Prior art]

The color image reading method used by the document reading unit (reader) in conventional color copying machines, etc. is to generate color separation signals of three colors, B (blue), G (green), and R (red), by one scan of the document. By obtaining data and temporarily storing these signal data in a predetermined memory before performing multicolor printing, and by scanning the original multiple times corresponding to each of the three primary colors of B, G, and H mentioned above, Some print in multiple colors.

In the former one-scan method, three scans can be made simultaneously by one scan.
Since color signal data is obtained, there is no relative color shift at each scanning time point, but a relatively large capacity memory is required, resulting in a very high cost.

On the other hand, in the latter multiple-scanning method, a memory for secondary storage is not required, but the problem is the inconsistency in document reading for multiple scans.

This variation in document scanning (reading) is thought to be caused by changes in viscous resistance within the drive system of the document reading unit, changes in sliding friction and load, elongation of the drive wire, and vibrations in the drive system itself. .

This variation in document scanning appears as a color shift or a hue shift during printing, and humans have the characteristic of detecting these shifts with extreme sensitivity.

〔the purpose〕

The aim of the invention is to eliminate the above-mentioned drawbacks.

Another object of the present invention is to improve an image forming apparatus.

Another object of the present invention is to provide an image forming apparatus capable of producing high quality reproduced images.

A further object of the present invention is to provide an image forming apparatus that can efficiently reproduce images.

A further object of the present invention is to provide an image forming apparatus capable of reproducing images faithful to the original.

A further object of the present invention is to provide an inexpensive image forming apparatus.

A further object of the present invention is to provide an image forming apparatus with fewer misprints.

Another object of the present invention is to improve a color image forming apparatus.

Another object of the present invention is to provide an image forming apparatus capable of producing color reproduced images with less color shift.

A further object of the present invention is to provide an image forming apparatus that eliminates the inconveniences that occur during color image formation.

mulberry.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of the internal configuration of a color image forming apparatus to which the present invention can be applied. First, the printer side 50 will be explained. 1 is an electrophotographic photosensitive drum having a photosensitive layer such as amorphous selenium on its surface. and is rotatably supported by shaft 2,
Rotation is started in the direction of the arrow in the figure in response to a copy command signal from a control section, which will be described later.

Reference numeral 3 denotes a scanner, which includes a semiconductor laser (see FIG. 4) for exchanging electrical signals into optical signals, a rotating polygon mirror for horizontally scanning the photosensitive drum, and the like.

4 is a reflecting mirror that changes the optical path, and 5 is a developing unit that visualizes the latent image on the photosensitive drum 1 with toner. This developing device unit 5 includes yellow developing devices 5-1. Magenta developer 5-2. It is composed of a cyan developer 5-3 and a black developer 5-4. 6-1 and 6-2 are paper cassettes that store copy paper; 7 is a transfer drum that contacts the outer peripheral surface of the photosensitive drum 1 via the paper; 8 is a transfer charger that transfers a toner image onto the paper; 9 is a transfer charger that transfers a toner image onto the paper; A fixing device 10 fixes the toner image on the paper by heat and pressure bonding, and 10 is a tray that stores the fixed recording paper.

Further, 21 is a lamp, and 22 is a light receiver, both of which constitute a transfer drum reference position sensor 314 (see FIG. 4), which will be described later.

Next, to explain the leader side, 100 is the entire leader,
101 is an original table glass on which the original is placed; 102 is the original; 10
3 is a scanning table for scanning the original 102; 104 is the original 102;
An illumination lamp 105 illuminates the original 102
106 is a CC that converts the optical signal collected by the lens 105 into an electrical signal.
It is a D sensor. The above-mentioned components 104 to 106 are attached to the scanning table 103 and move together.

In the configuration described below, when a copy command is output from the control section (see FIG. 4), the photosensitive drum 1 starts rotating in the direction of the arrow R shown in the figure, and the home position sensor ill
As a result, the scanning platform 103 of the reader 100, which has been stopped at the home position, starts moving in the direction of the arrow Y shown in the figure.

Further, the document 102 placed on the document table glass 101 of the reader 100 is illuminated by the illumination lamp 104 on the scanning table 103.
The reflected light is imaged on the CCD sensor 106 through the SELFOC lens 105. At that time, the reflected light image is color separated by a color separation mosaic filter (not shown) on the CCD sensor, and the color image signal converted into an electric signal by the CCD sensor passes through an image processing circuit (not shown) and is then printed by a printer. The data is temporarily stored in a memory (not shown) for synchronization with the data. Note that this memory only needs to have a capacity that can store image data for a plurality of lines.

In this way, when the photosensitive drum l rotates in response to a copy command and the gripper position fi7a of the transfer drum 7 rotates to the sensor position consisting of the lamp 21 and the light receiver 22, the information from the above-mentioned memory is transferred to the rotating polygon as a video signal. Semiconductor laser in scanner device 3 including mirror (see Figure 4)
The optical information is inputted into the photosensitive drum 1 and converted into optical information, and the optical path of the converted optical information is changed by the mirror 4 and is irradiated onto the photosensitive drum l.

The optical information irradiated onto the photosensitive drum 1 is converted into a latent image by a known charging process, and then developed by the developer unit 5. This developing device unit 5 includes a yellow developing device 5-1 having yellow toner as described above.
, a magenta developer 5-2 having magenta toner, a cyan developer 5-3 having cyan toner, and a black developer 5-4 having black toner. The developing device is equipped with a drive device that rotates the entire developing device around a shaft so that a developed color can be obtained.

On the other hand, the recording paper is stored in the upper cassette 6-1 or the lower cassette 6-2, and is selectively loaded from either cassette in response to a paper feed signal output from the control unit according to the copy cycle. After the paper is fed, it is conveyed to the transfer drum 7, and wound around the transfer drum 7 with the leading edge of the paper sandwiched between the grippers 7a. The transfer drum 7 is the photosensitive drum 1
The transfer charger 8 transfers the toner image on the photosensitive drum l onto the paper by synchronizing the position of the paper on the transfer drum 7 and the position of the developed image on the photosensitive drum l. do. The same process is repeated for other colors, and the color images are transferred onto the same sheet of paper.

After all the transfers for each color are completed, the paper is separated from the transfer drum 7, the image is fixed on the paper by the fixing device 9, and then the paper is discharged onto the tray 10.

FIG. 2 is an enlarged view of the periphery of the photosensitive drum 1 described above. As shown in the figure, 10 points on the photosensitive drum 1 are the laser beam irradiation positions, 11 points are the development start points,
In addition, with 22 points as the transfer start point, the distance on the circumference of the drum l is teP o −P, and the distance between the points is Ll, Pi ~
Let the distance between points F2 be L2.

FIG. 3 schematically shows the scanning positional relationship of the scanning section 103 of the above-mentioned reader lOO. Here, point R8 is the home position, which is the upper position where the CCD sensor 106 is stopped. R
There is a reading start point (document leading edge position) Ro at a point downstream from H, R1, which will be described later, is located Lr1 away from this RO point, and R is further Lr2 away from R1.
There are 2 measurement points. Furthermore, there is a movement end point RE at a distance RL from the reference passing point R, described above.

It is assumed that the scanning speed of the scanning table 103 of the reader is υ, and the circumferential speed of the photosensitive drum 1 is V. Assuming that the time required for the photosensitive drum 1 to move the distance Ll shown in FIG. is calculated using the following formula.

TP1=L1/V (1) TP2=L2/
V (2) On the other hand, the scanning table 103 is moved by the distance @ L r 1 shown in FIG.
Trl, the time required for the scanning table 103 to move.
Assuming that the time required for Lr2 to move is Tr2, Trl and Tr2 are obtained by the following equation.

Trx=Lr1/v (3) Tr2=Lr2
/v (4) Here, if Tp1=Trl and Tp2=Tr2, the following relationship holds from the above equations (1) to (4).

L r 1 = −・L t (5) ■ L r 2 = −・L 2 (6) ■ In this example, the above-mentioned R1 and R2 are Determine the position.

Generally, the circumferential speed V of the photosensitive drum 1 is a constant speed, and the scanning speed υ of the scanning table 103 is a variable speed for zooming, so the R1 and R2 points are not fixed points, but are It is a variable point that is a function of υ. Therefore, to specifically find the R1 point and the R2 point, do the following: R1 point,
It is sufficient to detect the R2 point.

That is, the CPU 201, which will be described later, calculates the distance Lr1. based on the input magnification and the above equations (5) and (6). and distance Lr
2, I
I! #Lr1. Number of pulses Lnl, Lr corresponding to Lr2
32.

Therefore, when the scanning unit 103 starts scanning and passes the reading start point R, it starts counting the output pulses, and the points R1 and R2 are when the count values reach Lnl and Lnl+Ln2.

Note that since the distance from the home position RH to the reading start point RO is also determined in advance, the number of pulses corresponding to this distance can also be set in advance.

Therefore, the reading start point RO can be easily detected by counting pulses from the home position after the start of scanning.

Further, the number of output pulses when moving the distance #RL is assumed to be NL. Also, R1 and R2 from R0 point.

The time required for scanning to the RE point is T1°T2. T
e, these (7) TI, T2. Te is determined by the following formula.

L T e = -(9) Now, when the scanning unit 103 of the reader 100 passes the R0 point, the timer is set to 0 to start timing, and when the timer passes the subsequent R1, R2 and RE points, That is, R,
The pulses of the encoder of the scanning unit 103 are counted from Ln
1 pulse, Lnl+Ln2 pulse, and NL pulse, respectively. As te, these tl, t2. te is the reference time TI, T2 . T
Compare with e. Here, allowable errors are given to these reference time values to Tl±ΔT1, T2±ΔT2, and Tef:ΔTe, respectively, and these reference values and the above-mentioned measured elapsed times tl, t2. By comparing the value of te, each R,, R2, R of the scanning unit 103 of the reader 100
Determine the passing state at point E.

FIG. 4 shows an example of the circuit configuration of the control section of the image forming apparatus shown in FIG. Exchange is done using l10 (input/output)
This is done via boats 204 and 304.

In the reader control block 200, a CP for calculation control
U (central processing unit) 201. R that memorized the control procedure
OM (read only memory) 202 and RAM (random access memory) 203 that stores data etc.
10 boat 204 via a bus.

Also, a copy button switch 205 for instructing to start copying.
The copy start signal from the encoder 206 which detects the movement distance of the scanning unit 103 and the signal from the home position sensor ill which detects the home position are binarized into digital signals via comparators 207 and 209. 204. Furthermore, encoder 2
06 outputs a pulse signal in synchronization with the scanning of the scanning unit 103. Therefore, by counting the pulses output from the encoder 206, the scanning unit 103
scanning position can be detected.

On the other hand, the output signal from the I10 boat 204 on the reader side drives the motor 210 for driving the scanning unit 103 via the driver 211, and the document reading command RDS from the I10 boat 204 is input to the CCD sensor 106. C.C.
The image signal obtained from the D sensor is outputted as a video signal VPS to the outside of the reader control block 200 through an image processing circuit 213 and a synchronous memory 214.

The printer control block 300 also includes a CPU 301 for arithmetic control, a ROM 302 that stores control procedures. A RAM 303 that stores data and the like is connected to an I10 port 304 via a bus. Further, a signal from a transfer drum reference position sensor 314 (sensors 21 and 22 in FIG. 1) is binarized and inputted to the I10 port 304 via a comparator 315. On the other hand, I10 boat 304
Output signals from the driver 30B control the bias high voltage of the developing device 5 via the bias transformer 309, and

From the driver 311 through the high voltage transformer 312,
It controls the transfer charger 8 and also controls the developer activity motor 317 via the driver 316 .

Also, the print signal PS from the I10 port 304 is input to the AND gate 305 together with the above-mentioned video signal VDS, and the output from this AND gate 305 is input to the driver 3.
06 and is converted into an optical signal by a semiconductor laser 307.

FIG. 5 is a flowchart showing an example of the control operation by the CPU 201 described above. Next, an example of the operation of the image forming apparatus in the first embodiment will be described with reference to the flowchart of FIG.

First, in step 5101, wait until the copy button switch 205 is turned on.
Then, in the next step 5102, the
00(1) After notifying the CPU 301 of sequence activation, the counter i in the CPU 201 is set to 1 in step 5103.
Initialize to . Next, in step 5104, the reader 100
and starts scanning by the scanning unit 103 from the home position RH, and at the same time, in step 5105, based on the output from the encoder 206, the internal timer of the CPU 201 on the reader side is initialized to zero at the RQ point. This timer measures the elapsed time tl, t2. Used to measure te.

Further, in step 3108, the ccD 106 starts reading the original image, and in step 5109, the i-th color signal is output from the image processing circuit 213.
It is predetermined in advance that when =1, the color is yellow, when i=2, the color is magenta, when i=3, the color is cyan, and when i=4, the color is black.

Next, in step 5110, the first measurement point, R1 point (
The elapsed time E1 (see FIG. 3) is checked based on the number of pulses from the encoder 206, and in the first judgment step 5ii1, T
1-ΔTiltl.

Or if T1+ΔTl<t1, that is, the measured value t1
If it is determined that the difference between and the reference time T1 is greater than or equal to the allowable error 411, it is determined that scanning is abnormal and the process branches to step 5121.

When it is determined in step 5ill that the measured value t1 is within the range of T1±ΔT1, in step 5ill, the elapsed time t2 of point R2 (see FIG. 3), which is the second measurement point, is determined based on the number of pulses of the encoder 206. Next step 5
113, T2−Δr2>t2 or T2+Δ”r2<t
2, that is, if the difference between the measured value t2 and the reference time T2 is greater than or equal to the allowable error 412, it is determined that scanning is abnormal and the process branches to step 5122.

When it is determined in step 5113 that the measured value t2 is within the range of the reference value T2±ΔT2, the next step 511 is performed.
In step 4, the elapsed time te is checked at the RE point (see FIG. 3), which is the movement end point, based on the number of pulses from the encoder 206, and in the next step 5115, Te-ΔTe>te or Te+
If it is determined that ΔTent e, that is, if it is determined that the difference between the measured value te and the reference time Te is greater than or equal to the allowable error ΔTe, the process branches to an error processing routine (not shown). The error processing routine performs necessary processing such as displaying an error and stopping machine operation.

In the above-described determination step 5115, the measured value te is the reference value Te.
If it is determined that it is within the range of ±ΔTe, then in step 5116, a control signal is sent to the control unit 300 of the printer to move the i+1st developer 5 of the printer to the developing position of the photosensitive drum 1. Having received this control signal, the CPU 301 causes the driver 3 to rotate the developing device 5.
The command is given via 16. Here, when i = 1, yellow, when i = 2, magenta, when i = 3, cyan, i
It is predetermined in advance that when =4, it is black, and when i=5, it is yellow like i=1. For example, if i=1 and the yellow developing device 5-1 is used, moving the i+1st developing device in step 5116 described above means i=2, that is, the magenta developing device 5-2 is used. This means that it is rotated and placed at the developing position of the photosensitive drum 1.

Next, in step 5117, the reader scanning platform 1'03 is returned to the home position, and the next step Sl
At step 18, it is determined whether the value of the counter i has become 4 or more. If the value of the counter i is 4 or less, the counter i is incremented by 1 in step 5119, and then the process returns to step 5104 to repeat the same process as described above.

That is, in response to the change of i=2.3.4 in the counter i, the color separation is sequentially read out from the thickness/document, and the copying process for each color of magenta, cyan, and black is repeated. If the counter i becomes 4 or more after that, the current copying process is ended and the process returns to the first standby step 5lot.

Now, as mentioned above, when an abnormality is detected in steps 5ill and 5113, the process moves to steps 121 and 122, but in steps 121 and 122, the developing device 5
development bias.

A control signal is sent to the controller 300 of the printer to turn off the transfer high voltage of the transfer charger 8. As a result of checking the required scanning time on the reader side at each point R1 and R2 shown in Figure 3, when it is determined that there is an abnormality, the transfer paper is (
This is to prohibit the transfer of the image onto the paper to be copied. That is, if an abnormality is found up to point R1, which is the first measurement point, the developing bias is turned off to prevent the latent image from being developed, and furthermore, if an abnormality is found up to point R2, which is the second measurement point. In this case, the transfer high pressure is turned off and the developed image is not transferred.
123, the control block 3 of the printer is configured to stop the normal image forming cycle while keeping the transfer drum 7 rotating.
00 CPU 301, then step 5124
The reading of the reader 100 is stopped at step 51.
At step 25, the scanning table 103 of the reader 100 is returned to the home position. Then, step 5126
Now, compare the error counter j and the set value jc, and find out that the value of the error counter j (number of errors) is equal to the number of errors of the set value j
If the number is greater than c, the process branches to error processing (not shown).

If the error counter j does not exceed the set value jc, the value of the error counter j is increased by 1 in the next step 5127. Next, in step 8128, the gripper 7a of the transfer drum 7 arranges the transfer drum reference position sensor 314. The process waits until the gripper passes the specified position, and when it is detected by a signal from the control unit 300 that the gripper has passed the specified position, the printer is notified of restarting the image forming cycle in step 5129, and the process returns to step 5104. At this time,
Since the value of the i counter has not been updated, the reader outputs the same color and develops with the development color corresponding to that color.

With the above control procedure, when a scanning abnormality is detected on the reader side, the printer side does not transfer the image output at that time onto the paper, but moves the transfer drum to output an image in the same color again.

In the explanation of the above embodiment, the scanning error of the reader was investigated using the time required to output a set number of pulses, but conversely, Of course, the number of pulses applied may also be checked. In addition, although the position of each point Ro, Rt, and R2 on the reader side is determined by the number of pulses from the encoder, it is also possible to arrange a position sensor at each passing point. Control means may be added to detect whether the speed is too fast or too slow and change the speed of the motor during the primary scan.

In addition, in the embodiment of the present invention, 1. Although a color copying apparatus equipped with a so-called digital reader of a digital reading type has been described, it goes without saying that the present invention can also be applied to a color copying apparatus equipped with an analog type optical reading device.

As explained above, in the first embodiment, the scanning speed is constantly monitored for multiple scans.

When an abnormality is detected in the scanning speed, the scanning is repeated again, so that a color print without color shift or hue shift can be obtained, and unnecessary failed prints are not produced.

That is, in the first embodiment, when the reader side detects that a color shift exceeding the allowable value has occurred, at the time of the detection,
The image forming cycle on the printer side is interrupted, the reader outputs the same color again, and if the color shift is within the tolerance value, the interrupted image forming cycle is restarted and continued to print the required image. It is configured to complete the forming process. In this case.

Detection of color shift is performed indirectly by providing a predetermined scanning section on the reader side and comparing the travel time of that section with a reference value.

On the other hand, the printer side includes a transfer drum device, and when color misregistration is detected on the reader side, the image forming operation, specifically, one of the steps of development and transfer, is prohibited.
In addition, the transfer drum is driven at least once, and when outputting the next image, a printing operation is also performed using a developer of the same color as the previous one.

Next, a second embodiment of the present invention will be described.

Incidentally, FIG. 1, FIG. 2, and FIG. 4 can also be used in the second embodiment. Therefore, detailed description of these drawings will be omitted.

FIG. 6 schematically shows the scanning positional relationship of the scanning sections of the reader 100. Note that the same parts as in FIG. 3 are given the same reference numerals. Here, the RH point is the home position, which is the [h position of the CCD sensor 106. Further, Rs is a reference passing point set beyond the point where the scanning speed of the scanning table 103 of the reader becomes constant. From this reference passing point Rs
There is a reading start point (document leading edge position) Ro at the point where ro* is reached, and R, which will be described later, is at a position Lr1 away from this RQ point.
1. And there is a measurement point of R2 at a position further Lr2 away from R1. Further, there is a movement end point RE at a distance RL from the above-mentioned reading start point RQ.

It is assumed that the scanning speed of the scanning table 103 of the reader is υ, and the circumferential speed of the photosensitive drum 1 is V. If the time required for the photosensitive drum l to move the distance Ll shown in FIG. 2 is Tpl, and the time required for the photosensitive drum 1 to move the distance L2 shown in FIG. It can be obtained using the following formula.

TP1=L1/V (10) TP2=L2
/V (11) On the other hand, the distance shown in Fig. 6 @
If the time required for the scanning table 103 to move by L r 1 is Trl, and the time required for the scanning table 103 to move a distance L r 2 is Tr2, then this Trl and T
r2 is determined by the following formula as described above.

Tr1=Lr1/v (12) Tr2=,L
r2/v (13) Here, Tp1=Tr1
and Tp2=Tr2, the above equations (10) to (13
), the following relationship holds.

L　r　1=　--L　　　　　(14)■ Lr　2　=　-Contest L　2　　　(15)■ The above formula (14) also applies to the second embodiment.

The above R1 and R2 are set so that the relationship (15) holds true.
determine the position of

As mentioned above, in general, the circumferential speed V of the photosensitive drum 1 is constant, and the scanning speed υ of the scanning table 103 is variable for zooming, so the R1 and R2 points are not fixed points, but the above equation It is a variable point that is a function of υ. Therefore, in order to specifically find the R1 point and the R2 point, the pulses of the encoder that operates in synchronization with the scanning of the scanning unit 103 are used as described above.

That is, the CPU 201, which will be described later, calculates the distance Lr1. based on the input magnification and the above equations (14) and (15). Calculate Lr2 and use this calculated value as 7 dresses to calculate RA.
M etc. into a table (not shown), and from this table, the path number L n corresponding to the distances Lr1 and Lr2 is calculated.
1 +Ln2. Then, by canting these pulse numbers Lnl and Ln2 as described above, point R1 is reached, R
Detect two points.

Note that since the distances from the home position R1 (from the reading start point R, to the reference passing point Rs) are also determined in advance, the number of pulses corresponding to these distances can also be set in advance.

Therefore, after the start of scanning, the points RO and Rs can be easily detected by counting pulses from the home position.

Further, the number of output pulses when moving distances LrO and RL are respectively Ln□ and NL. Also, RQ from Rs point which is the reference passing point.

The time required to reach R1, R2, and RE points is To and T, respectively.
1', 72', Te', these (7) To,
Tl ′, 72 ′, and Te ′ are determined by the following equations.

Lr□ TO= -(16) υ Te'=To+RL Now, the reference passing point ° of Rs is set by the scanning unit 10 of the reader 100
When 3 passes, the timer is set to 0 and starts counting, and the subsequent RQ and R1.

When passing R2 and RE points, that is, counting the encoder pulses from Rs point, Ln□ pulse, 'L n
□ + Ln 1 pulse, LnO+Ln 1+LH
2 pulse and the elapsed time when Ln□+N1 pulse are reached are to+t1' and t2', respectively.

Compare with the reference times To, 71', T2', Te''. Here, give a tolerance to these reference time values,
To±Δ”ro, “rl”±ΔTl', T2, respectively
'±ΔT2' and Te'±ΔTe', and these reference values and the previously measured elapsed times t□, t1", t2"
, te', the reader 10
The teno passing state of each Ro, R1, R2, and RE point of the 0 scan is determined.

FIG. 7 is a flowchart showing an example of control operations by the CPUs 201 and 301. Next, an example of the operation of the image forming apparatus in the second embodiment will be described with reference to the flowchart in FIG. 7 and FIGS. 4 and 6.

First, in step 5lot, wait until the copy button switch 205 is turned on, and then the switch 205 is turned on.
Then, in the first step 5102, the printer control unit 30
After notifying the CPU 301 of No. 0 of sequence activation, the counter i in the CPU 201 is initialized to 1 in step 5103. Next, in step 5104, the reader 100 is started, and the scanning unit 103 starts scanning the home position R).
The internal timer of the CPU 201 on the reader side is initialized to zero at Rs based on the output from the encoder 206 in step 5105.

Furthermore, in the next step 5106, the reading starting point of RO (
The elapsed time to (see FIG. 6) is checked based on the number of pulses from the encoder 206.
-ΔTO>to, or TO+ΔTo<to, that is, the difference between the measured value 1 (, and the reference time To is the tolerance 61
If it is determined that it is 0 or more, it is determined that scanning is abnormal and the process branches to step 5120.

When it is determined in step 5107 that the measured value to is within the range of the reference value TO±ΔTo, the process advances to step 5108 to start reading the original image by the CCD 106, and in step 5109, the i-th color signal is subjected to image processing. circuit 213
Output from. For example, when i=1, yellow, i=2
It is predetermined in advance that when , it is magenta, when i=3 it is cyan, and when i=4 it is black.

Next, in step 5ilo, the second measurement point, R1 point (
The elapsed time t1' (see FIG. 6) is checked based on the number of pulses from the encoder 206, and in the next judgment step 5ill,
T1'-ΔT1')tl', or T1'+ΔTl'
<tl', that is, the measured value tl' and the reference time Tl
If it is determined that the difference from ' is greater than or equal to the allowable error ΔT1, it is determined that scanning is abnormal and the process branches to step 5121.

When it is determined in step 5ill that the measured value t1' is within the range of T1'+ΔTl', in step 5112 the elapsed time t of point R2 (see FIG. 6), which is the third measurement point.
2' is checked based on the number of pulses of the encoder 206, and in the next step 5113, if T2'-ΔT2'>t2' or T2'+ΔT2''<t2', that is, the measured value t2'' and the reference time T2' are determined. The difference is the tolerance ΔT2”
If this is the case, it is determined that scanning is abnormal and the process branches to step 5122.

In step 5113, the measured value t2' becomes the reference value 72'-±Δ
When it is determined that it is within the range of T2', in the next step 5114, the elapsed time fli te ' is checked based on the number of pulses from the encoder 206 at the RE point (see FIG. 6), which is the movement end point, and the next step is Step S 115 Te
'-ΔTe'>te' or Te'+ΔTe'
', that is, if it is determined that the difference between the measured value te' and the reference time Te' is greater than or equal to the allowable error ΔTe, the process branches to an error processing routine (not shown). The error handling routine performs necessary processing such as error display and stopping of machine operation.

In the above-described determination step 5115, the measured value te' is determined to be the reference value T.
If it is determined that it is within the range of e'±ΔTe', then in step Sl 16, the developer 5 at the i+1 slot of the printer is
A control signal is sent to the controller 300 of the printer to move the photosensitive drum 1 to the developing position. Upon receiving this control signal, the CPU 301 issues a command via the driver 316 to rotate the developing device 5.

Here, when i = 1, it is yellow, when i = 2, it is magenta, when i = 3, it is cyan, and when i = 4, it is black, and f = 5 is yellow as well as i = 1. For example, if i=1 and the yellow developing device 5-1 was used, moving the i=1st developing device in the above step 511.6 means that i=2, i.e. This means that the magenta developing device 5-2 is rotated and placed at the developing position of the photosensitive drum 1.

Next, in step 5117, the reader scanning table 103 is returned to the home position, and the next step Sl
At step 18, it is determined whether the value of the counter i has become 4 or more. If the value of counter i is less than or equal to 4, step S
After incrementing the counter i by 1 at t19, the process returns to step 5104 and repeats the same process as described above.

That is, in response to the change of i=2.3.4 in the counter i, color separation is sequentially read out from the original, and the copying process for each color of magenta, cyan, and black is repeated. Then counter i
If the value becomes 4 or more, the current copying process is ended and the process returns to the first standby step 5101.

Now, as mentioned above, steps 5107, 5111.51
If an abnormality is detected in step 13, steps 120 and 12
1, 122, but steps 120, 121, 1
At step 22, a control signal is sent to the printer controller 300 to turn off the laser 307, the developing bias of the developing device 5, and the transfer high voltage of the transfer charger 8, respectively.

This means that the scanning time required on the reader side is l(0
, R1, and R2, and when it is determined that there is an abnormality, the image forming element on the photosensitive drum 1 is prohibited from outputting, thereby prohibiting the image from being transferred to the transfer paper (copying paper). This is to do so. That is, if an abnormality is found before point R0, which is the reading start point, the output of the laser 307 is prohibited to prevent latent image formation.
If an abnormality is found up to point R1, which is a fixed point, turn off the developing bias to prevent the latent image from being developed, and if an abnormality is found up to point R2, which is the third measurement point, the transfer The configuration is such that the high voltage is turned off so that the developed image is not transferred. Next, in step 5123, the CP of the printer control block 300 is activated so as to stop the normal image forming cycle while keeping the transfer drum 7 rotating.
A notification is sent to U301, and then, in step 5124, reading by the reader 100 is stopped, and then, in step 5125, the scanning table 103 of the reader 100 is returned to the home position. Subsequently, in step 5126, error counter j and set value jc are compared.

If the value of the error counter j (number of errors) exceeds the set value of the number of errors jC, the process branches to error processing (not shown).

If the error counter j does not exceed the set value jc, the value of the error counter j is incremented by 1 in the next step 5127. Next, in step 5128, wait until the gripper 7a of the transfer drum 7 passes the specified position where the transfer drum reference position sensor 314 is arranged, and when the control unit 300 detects that the gripper has passed the specified position, step 5129 In step 5104, the printer is notified of the restart of the image forming cycle, and the process returns to step 5104. At this time,
Since the value of the i counter has not been updated, the reader outputs the same color and develops with the development color corresponding to that color.

With the above control procedure, when a scanning abnormality is detected on the reader side, the printer side does not transfer the image output at that time onto the paper, but moves the transfer drum to output an image in the same color again.

In the explanation of the above embodiment, the scanning error of the reader was investigated using the time required to output a set number of pulses, but conversely, 1. Of course it is one of the best. Also, Rs, Ro, R1, on the leader side
Although the position of each point of R2 is determined based on the number of pulses from the encoder, it is also possible to arrange a position sensor at each passing point. or.

Control means may be added to detect when the scanning speed is too fast or too slow and change the speed of the motor during the next scan.

Furthermore, for the sake of explanation, in the embodiment, an example was disclosed in which the laser is switched to OF or F when a scanning mark is detected at the R0 point (reading start point), but the purpose is to prevent image transfer from occurring. If this is the case, the developing bias or transfer high pressure may be turned off at this point (RO).

Also, the distance from the reference passing point Rs to the reading start point RQ @L
Although rO is constant, it is not limited to this, and the eighth
As shown in the figure, the location may be determined depending on the location of the document.

That is, when the document 102 becomes younger by L downstream from the R0 point, the reading start point Ro' is set to a point Lro' away from the Rs point, that is, a point Lr+)+L. In this case, let Ln□' be the number of pulses required to scan from point Rs at a uniform speed υ until finding the original position ♂ at point RO'. As mentioned above, the standard number of pulses when moving Lr□ is LnO
, the standard time (reference time) required for this movement is To', so the new standard time TO for Ln(+' can be calculated by the following equation).

This standard time To' plus the tolerance ±ΔTO'
What is necessary is to compare the actual time tO' required to move Lr□' with '±ΔTo'. Similarly, if the end point of the scanning movement is the actual document end point RE', then R
The time and number of pulses corresponding to the distance RL' from Q' to point RE' can be detected and calculated.

In each of the embodiments described above, if an abnormality in the league is detected before the reproduced image is actually transferred onto the transfer paper, the transfer is stopped and the same image forming operation is repeated again. However, if an abnormality in the league is detected after the actual transfer operation has started, the image forming operation may be stopped and the transfer paper may be ejected. Further, at this time, the image forming operation may be restarted from the beginning.

Furthermore, the present invention is applicable not only to color copying machines, but also to copying machines equipped with facsimile or page speed copying functions, for example. Here, the page continuous copying function refers to a function that scans different portions of the original platen twice in one operation to form an image twice.

〔effect〕

As described above, according to the present invention, it is possible to prevent unnecessary printing or unnecessary image forming operations.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the internal configuration of a color image forming apparatus to which the present invention can be applied, and FIG. 2 is an enlarged view showing details of the drum section and developing section in FIG. 1. FIG. 3 is an explanatory diagram showing the scanning positional relationship of the scanning unit of the league in FIG. 1. FIG. 4 is a block diagram showing an example of the circuit configuration of the control system of the device in FIG. 1. FIG. 6 is an explanatory diagram showing the scanning positional relationship of the scanning unit on the league side in the second embodiment; FIG. 7 is a flowchart showing an example of the control operation in the second embodiment; FIG. 8 is an explanatory diagram showing the third embodiment. In the figure, 101--m-original table glass, 102--one original, 1
03---1 Scanning stand, 111---Home position sensor, 106---CCD safety, 200---Reader control block, 300---Printer control block, 201, 301---1 -CPU, 202, 30
2---ROM, 204,304---I10 port,
205--11 copy button switch, 206--
Encoder, 307-to-semiconductor laser, 210, 31
7--It is a motor.

Claims (1)

[Scope of Claims] A document scanning device that scans a document multiple times to form one reproduced image, and an image forming device that forms the document image scanned by the document scanning device on a recording medium and transfers it onto a transfer paper. In an image forming apparatus having means, when a first abnormal scanning state of the original scanning means is detected, causing the original scanning means to perform rescanning, and detecting a second abnormal scanning state of the original scanning means. An image forming apparatus characterized in that, when detected, the image forming operation by the image forming means is stopped and the transfer paper is ejected.